1. Field of the Invention
The present invention relates to a probe used for dropping a sample solution eluted from a liquid-transporting mechanism such as a high-performance liquid chromatograph as droplets from the tip thereof onto a plate such as a micro-plate or a sample plate, and a sample pretreatment apparatus including such a probe.
2. Description of the Related Art
Conventionally, in a case where an eluant separated by a separation column of a high-performance liquid chromatograph is automatically dropped on to a sample plate, for example, for a MALDI-TOF-MS (Matrix assisted laser desorption ionization time of flight mass spectrometry) so as to be fractioned and collected, a component to be measured is separated by a high-performance liquid chromatograph (HPLC) and connected to a UV detector from the tip of the separation column through a pipe (see Japanese Unexamined Patent Publication No. 2004-184149).
Normally, the amount of a droplet to be dropped on to a sample plate for the MALDI is 2 μL at the most, and in order to allow such a small amount of a droplet to drop, the liquid chromatograph uses not a normal flow rate of 1 mL/min, but a micro-scale of 5 μL/min or a nano-scale of 200 nL/min, as the flow-rate scale. This is because in an attempt to drop at every 1 μL at 1 mL/min, spots (dropping) are for every 0.001 min, and this operation is virtually impossible.
In a case of a normal flow-rate scale, a pipe having an inner diameter of about 0.3 mm is used; however, in order to ensure a proportional relationship between the flow-rate scale and the pipe inner diameter and to limit the dispersion of a component separated by a separation column to a minimum level, the pipe inner diameter is further narrowed to 1.5 μm in the micro-scale, and to 60 nm in the nano-scale.
However, in actuality, the pipe having an inner diameter in a range from 20 to 50 μm is used by taking into consideration clogging of the pipe due to contamination (foreign matters). For example, upon application of a pipe having an inner diameter of 50 μm, the pipe capacity becomes 1 μL when the pipe length is 500 mm.
In a case of the normal flow-rate scale, the size of the pipe capacity corresponds to a pipe capacity of 5 mL with respect to the flow rate of 1 mL/min, and due to such a large pipe capacity, the target component separated by the separation column is dispersed. In a case where the analysis is carried out by using a flow rate in the nano-scale, the influence caused by the pipe capacity becomes more conspicuous.
In a case of using the MALDI-TOF-MS, there is a demand that ideally, a single target component, separated by the high-performance liquid chromatograph, should be dropped on to a single well.
Such a demand is given not only in the preparation of a sample for the MALDI-TOF-MS, but also in the addition of an additive such as a reaction solution to an eluent from the high-performance liquid chromatograph.